Gas turbine combustors are the subject of continual improvement, to provide better cooling, better mixing, better fuel efficiency, better performance, etc. at a lower cost. Also, a new generation of very small gas turbine engines is emerging (i.e. a fan diameter of 20 inches or less, with about 2500 lbs. thrust or less), however larger designs cannot simply be scaled-down, since many physical parameters do not scale linearly, or at all, with size (droplet size, drag coefficients, manufacturing tolerances, etc.). There is, therefore, a continuing need for improvements in gas turbine combustor design.